1. Field of the Invention
The present invention relates generally to the field of improving the heat transfer resistance of a paneling system in which insulation material is confined between construction members, and more particularly, but not by way of limitation, to a frameless enclosure assembly providing improved insulating qualities to pre-engineered buildings and the like.
2. Discussion of the Prior Art
The pre-engineered building industry has developed into a multi-billion dollar segment of the building construction industry in the United States, and it has experienced an increasingly greater share of the construction industry budget throughout the world. The established method of erecting the roof or wall of a pre-engineered building is to erect the primary structural members; attach the secondary structural members to the primary structural members; secure the appropriate bracing members; roll blanket-type insulation across the secondary structural members and temporarily secure the insulation in place by weights or some securing means; dispose panel members over the blanket insulation; and connect the panel members and secondary structural members together by fasteners that penetrate the blanket insulation.
Typically, attachment of roof panel members is performed by workmen who stand on top of the roof panel members and insert fasteners through the roof panel members to attach them to the underlaying secondary structural members (sometimes referred to as purlins). Similarly, the wall panel members are attached to the underlaying secondary structural members (sometimes referred to as girts) by externally positioned workmen who must insert fasteners through the wall panel members and anchor them to the girts.
The insulation of a pre-engineered building in the above described manner presents a major problem in the construction of such buildings. As the fasteners are installed through the panel members, the underlaying blanket insulation is compressed between the panel members and the underlaying secondary structural members as the fasteners are attached thereto. This compression is undesirable, as such reduces the thermal effectiveness of the blanket insulation. Furthermore, the purpose of the fasteners is to secure the panel members and to transfer load from the panel members, which is usually the exterior sheathing, to the secondary structural members. This load creates stresses that may be tension, shear or compressive stress. As to the latter, compressive stress is created by inwardly directed live loads which are transferred through the blanket insulation, which is normally a compressible but non-elastic material. As the panel members move relative to the secondary structural members during the life of the building, looseness occurs around the fasteners, and it is difficult, if not impossible, to maintain a water tight connection at the points where the fasteners penetrate the panel members.
Prior art solutions offered to this problem of compressed insulation have included the provision of elastic insulation boards that are disposed between the insulation and the panel members. These insulation boards are located such that the fasteners are caused to penetrate the boards before penetrating the insulation, and as the fasteners are anchored to the underlaying secondary structural members, the insulation boards spread the compressive load of the fasteners over a larger area of the insulation to reduce the amount of compressive reduction of the insulation thickness. While this is an improvement over the previously described method, it still has a number of shortcomings. Among these is the fact that the blanket insulation is still compressed between the insulation boards and the underlaying secondary structural members, and since the insulation boards are normally made of compressible material, the insertion of the fasteners still tends to crush the insulation boards as well. This in turn results in a number of detrimental features, which are discussed in more detail in my earlier U.S. patent application entitled "Support Spacer Apparatus", Ser. No. 093,173, filed Nov. 13, 1979.
One serious problem with the use of insulation boards in addition to the blanket insulation is the creation of void spaces between the panel members and the blanket insulation at the edges of the insulation boards as such void spaces are detrimental from a heat transfer resistance standpoint. Further, the insulation of panel members with the added insulation boards has complicated the erection of pre-engineered buildings. The natural elements, including wind, frequently dislodge the insulation boards before the overlaying panel members can be properly positioned, or the insulation boards are dislodged by the panel members as the panel members themselves are being positioned.
The pre-engineered building industry has adopted the use of "diaphragm action" to resist wind loads on a building. Diaphragm action requires that force parallel to the plane of a panel be transferred through the fastening system to the underlaying secondary structural members. While the use of insulation boards has helped somewhat in regard to increasing the thermal effectiveness of the blanket insulation, it remains that the diaphragm action on the panel members causes the load to be transferred directly through the insulation, and the problem of maintaining watertight seals around the fasteners continues even with the use of such insulation boards.
The patent issued to Taylor, U.S. Pat. No. 3,394,516, taught the use of a spacer between the panel members and the secondary structural members to prevent the panel members from being pulled so close to the secondary structural members as to crush or compress the insulation. The Taylor spacer had a plurality of pointed legs that served to penetrate the insulation, and sheet metal screws passed through the panel members and the spacers to secure the panel members to the secondary structural members. However, while the Taylor spacer substantially reduced the amount of compressive reduction of the insulation, the Taylor spacer afforded a heat conducting bridge between the secondary structural members and the panel members.
While the Taylor spacer did provide a mechanism for transferring the stress between the panel members and the supporting secondary structural members, the spacer legs of the Taylor spacer, being independent to the fasteners, could more to some degree relative to the supporting secondary structural members, thus permitting some fretting of the fasteners with the panel members. This movement can lead to a deterioration of both the watertightness of the fasteners and the thermal barrier as the insulation next to the pointed legs is spread about. Also, depending upon the type of vapor barrier provided by the insulation, penetration of the insulation by the Taylor spacer in some instances may prove difficult to effect without substantially compressing the insulation material while piercing the insulation facing, such as when a vinyl facing is provided. Finally, installation of the Taylor spacer required the placement of appropriately disposed holes in the secondary structural members for receiving the screw members which serve to secure the spacer.
There have been other problems associated with the above described prior art technique of insulating pre-engineered buildings. Clearly, it is highly desirable to create a substantially uniform, effective resistance to heat transfer in building roofs and walls, and this may be accomplished by applying a uniform thickness of insulating material over the building surface, usually referred to as the "building envelope". A uniform resistance eliminates thermal short-circuits, reducing air conditioning and heating costs.
It is clear that the use of compressible blanket insulation has in the past had some inherent disadvantages, various other materials have been pursued in an effort to provide uniform, effective resistance to heat transfer throughout the walls and roofs of buildings, including pre-engineered buildings. However, this has been difficult since a building is basically a structural element, and materials having good structural characteristics are normally poor thermal insulators. Good thermal insulators, on the other hand, normally.are structurally weak. Because of this, designers have attempted to interweave materials having good structural characteristics with those which have good insulating characteristics to create a more effective building envelope. Among the various prior art solutions are structural surfacing materials such as steel or concrete with "spray-on" materials such as isocyanurate or similar foams field-applied on the inside or outside of the structural surface material. Spray-on materials have the potential advantage that they cover the building surface, regardless of its configuration, in a relatively uniform manner. While this method eliminates thermal short-circuits, the spray-on materials also have numerous shortcomings. Among these are high costs resulting from the field labor involved, poor quality control which frequently leads to inadequate bonding so that the insulation often delaminates, and project delays because of inclement weather conditions.
Another prior art solution is represented by the paneling systems which are factory or field assembled and composed of various combinations of materials. Among the paneling systems that have been tried are laminated systems composed of one or more rigid facing materials with an appropriate semi-rigid insulation attached to the rigid material for support. These systems usually have metallic facings and use foams such as urethane. A few systems have been designed which are composed of only one facing material, such as plywood, and one semi-rigid insulation, such as urethane. While these paneling systems have been generally acceptable, their cost is high and they are subject to damage during transportation and erection. In most instances, thermal short-circuits, while lessened, still exist. Examples of such panel systems may be found in U.S. Pat. Nos. 4,147,004; 4,104,840; 3,672,951; 3,667,180; 3,535,844; 3,479,784; and 3,399,503.
Other paneling systems of this type have used relatively dense batt insulation of the glass fiber type and usually rely on perimeter framing of some type to hold the insulation in place. The insulation either has to be strong enough to support its own weight without gradual crushing, or friction support must be employed. Friction from the insulation itself is often inadequate to hold the insulation in place, and as a result of vibration from wind or transportation, the insulation often becomes dislodged. The insulation itself is structurally weak and even pins or other support protrusions into or through the insulation will not serve to prevent the insulation from settling when it is used in a vertical wall. In the past, this type of paneling system has been relatively expensive and has not solved the problem of preventing thermal short-circuits through the insulation. The perimeter framing usually consists of two sides and one each top and bottom member. These type of paneling systems are sometimes referred to as sandwich panels as they normally have front and back covers, and in most instances, present thermal inefficiencies at the panel sides and ends. In an attempt to reduce these thermal inefficiencies, the prior art abounds with complex side joints which make the sandwich panel solution even more expensive. Examples of such paneling systems may be found in U.S. Pat. Nos. 4,0120,123; 4,107,892; 3,747,583; and 3,377,760.
Of all the insulation methods attempted, the use of compressible blanket insulation remains to be the least expensive and most effective means of insulating a building structure, which accounts for its wide acceptance in the building industry. Of course, blanket insulation is totally effective only if the design of the building structure provides for the use of the insulation in such a manner that the blanket insulation's full thickness is maintained, and it remains dry. Typical blanket insulation used in the building industry consists of a lightweight, highly compressible, structurally weak insulating material laminated to a lightweight, relatively high tensile impervious facing membrane that is used to place, support and maintain the insulation in a predetermined position. The combination of insulation layer and facing material is normally positioned and maintained in place by applying tensile or restraining forces to the facing material through a friction connection. In normal practice, that friction connection compresses the insulation, as discussed hereinabove, and this compression materially reduces the effectiveness of the insulation. Past attempts to use the facing membrane of the blanket insulation as a structural retainer have met with limited success, such as in U.S. Pat. No. 4,147,003. Serious thermal inefficiencies are presented by the required compression of the insulation at each side of the panel, resulting in serious thermal inefficiencies.
Among the principal reasons that past uniform thickness paneling systems have not used the relatively inexpensive, but effective faced blanket insulation in its full thickness, is that prior art attempts have not had an effective means of applying tensile or holding force to the insulation facing. In most instances, the faced blanket insulation has been clamped between the panel and the underlaying structural members. This serves the dual purpose of transferring load from the panel through the insulation to the underlaying structural system while securing the insulation in place. However, the clamping of the insulation between the panel and the underlaying structural system results in serious thermal inefficiencies. In addition, this method of clamping the facing material results in non-uniform tensile stress being created in the facing material, and this leads to wrinkles across the facing of the blanket insulation which, when the facing material is visible in the interior of the building, provide poor appearance. This non-uniform tensile stress results because the panel is normally compressed against the underlaying structural members by fasteners, and the beam strength of the panel between fasteners is insufficient to exert adequate frictional force on the insulation facing to spread the tensile load in the facing uniformly across the width of the insulation.
A commonly practiced technique is to clamp blanket insulation at the base of a wall panel, which results in compressing the insulation and reducing its thickness at its base. In most instances, the insulation is simply cut just below the bottom of the wall panel and the end of the insulation is exposed to rain, snow and other moisture. As a result, the insulation "wicks" water into the body of the insulation for a considerable distance along its length. This water further decreases the thermal efficiency of the insulation, and also results in corrosion of panel, base angle and other supporting parts. The uneven tensile stress exerted on the base of the blanket insulation also has a detrimental effect in that those areas subject to excessive stress tear and are more easily punctured, resulting in poor appearance and inadequate vapor barriers.